"A parish in the Union of Ruthin, hundred of Yale, county of Denbigh; 6 miles (SE) from Ruthin, containing 378 inhabitants."
[ A Topographical Dictionary of Wales, 1833 & 1849, Samuel Lewis]
The ancient parish at one time comprised the three townships of Llandegla, Trefydd Bychain, and Bodlywydd; however, Bodlywydd has long since been incorporated into the parish of Llanelidan.
By an Order in Council, gazetted on 11 March 1887, part of the parish of Llanarmon yn Iâl was transferred to the parish of Llandegla. Archdeacon Thomas defines the area transferred thus :
"That portion of Llanarmon lying south of a line drawn from Pont Ystyllod through Rhos Isa and Perthichwareu, and taking in also a portion of Bodidris township (including the Hall) and the Gwernoliaid, as far as Llyn Maelor."